Climate Change
Climate Change Indicators in the United States
This figure shows worldwide emissions of carbon dioxide, methane, nitrous oxide, and several fluorinated compounds from 1990 to 2005. For consistency, emissions are expressed in million metric tons of carbon dioxide equivalents. These totals do not include emissions due to land use change or forestry because estimates are not available for the most recent years.
* HFCs are hydrofluorocarbons, PFCs are perfluorocarbons, and SF6 is sulfur hexafluoride.
Data source: World Resources Institute, 2009 2
This figure shows worldwide greenhouse gas emissions by sector from 1990 to 2005.* For consistency, emissions are expressed in million metric tons of carbon dioxide equivalents. These totals do not include emissions due to land use change or forestry because estimates are not available for the most recent years.
* Note that the sectors shown here are different from the economic sectors used in U.S. emissions accounting (see the U.S. Greenhouse Gas Emissions indicator). Emissions from international transport (aviation and marine) are separate from the energy sector because they are not part of individual countries' emission inventories.
Data source: World Resources Institute, 2009 3
This figure shows carbon dioxide emissions from 1990 to 2005 for different regions of the world. These data do not include emissions attributable to land use, land use change, or forestry.
Data source: World Resources Institute, 2009 4
Key Points
- In 2005, the world is estimated to have emitted over 38,000 million metric tons of greenhouse gases, expressed as carbon dioxide equivalents. This represents a 26 percent increase from 1990 (see Figures 1 and 2).
- During the period from 1990 to 2005, global emissions of all major greenhouse gases increased (see Figure 1). Methane emissions rose the least—10 percent—while emissions of fluorinated compounds more than doubled. Emissions of carbon dioxide increased by 31 percent, which is particularly important because carbon dioxide accounts for nearly three-fourths of total global emissions.
- Energy use is the largest source of greenhouse gas emissions worldwide (about 73 percent of the total), followed by agriculture (16 to 17 percent) (see Figure 2).
- In the United States, changes in land use and forestry represent a net "sink" for greenhouse gases, meaning they absorb more greenhouse gases (for example, through the net growth of forests) than they emit. On a global scale, however, these activities represent an additional source of greenhouse gases due to factors such as human-caused destruction of forests. 1
- Greenhouse gas emissions are increasing faster in some parts of the world than in others (see Figure 3).
Background
Every country around the world emits greenhouse gases, meaning the root causes of climate change are truly global. Some countries produce more greenhouse gases than others, however, depending on factors such as economic activity, population, income level, land use, and weather conditions. Tracking greenhouse gas emissions worldwide provides a global context for understanding the United States' role in addressing climate change.
About the Indicator
Like the U.S. Greenhouse Gas Emissions indicator, this indicator focuses on emissions of gases covered under the United Nations Framework Convention on Climate Change: carbon dioxide, methane, nitrous oxide, and several fluorinated compounds. These are all important greenhouse gases that are influenced by human activities, and the Convention requires participating countries to develop and periodically submit an inventory of emissions.
Data and analysis for this indicator come from the World Resources Institute's Climate Analysis Indicators Tool (CAIT), which compiles data from greenhouse gas inventories developed by EPA and other agencies worldwide. Global estimates for carbon dioxide are published annually, but estimates for other gases such as methane and nitrous oxide are available only every fifth year.
This indicator tracks emissions of greenhouse gases according to their global warming potential, a measure of how much a given amount of the greenhouse gas is estimated to contribute to global warming over a selected period of time. For the purposes of comparison, global warming potential values are given in relation to carbon dioxide and are expressed in terms of carbon dioxide equivalents.
Indicator Confidence
Like the U.S. Greenhouse Gas Emissions indicator, this indicator does not include emissions of a number of gases that might affect climate but are not covered under the United Nations Framework Convention on Climate Change. For example, this indicator excludes ozone-depleting substances such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons, which have high global warming potentials, as these gases are being phased out under an international agreement called the Montreal Protocol. There also are a variety of natural greenhouse gas emission sources; however, this indicator includes only man-made and human-influenced greenhouse gas emissions.
Global emission inventories for gases other than carbon dioxide are limited. Data are only available at five-year intervals, and the most recent year—2005—represents a set of projections. The United Nations Framework Convention on Climate Change database has more comprehensive data; however, these data are available only for developed countries that are parties to the Convention—a group that accounts for only about half of global greenhouse gas emissions. Thus, to provide a more representative measure of global greenhouse gas emissions, this indicator uses the broader CAIT database.
Data Sources
Data for this indicator came from the World Resources Institute's CAIT database, which is accessible online at: http://cait.wri.org. CAIT compiles data that were originally collected by organizations such as the United Nations, International Energy Agency, EPA, and U.S. Carbon Dioxide Information Analysis Center.
Indicator Documentation
- Download related technical information PDF (7 pp, 54K)